The inventive concept relates to a semiconductor memory device, and in particular, to a three-dimensional semiconductor memory device.
In the case of semiconductor devices, increased integration is especially desired because integration is an important factor in determining product prices. In particular, higher integration of semiconductor devices is required to satisfy consumer demands for electronic products that offer superior performance and yet are relatively inexpensive. In the case of typical two-dimensional or planar semiconductor devices, integration is mainly a factor of the area occupied by a unit memory cell of the devices. Therefore, the degree to which two-dimensional or planar semiconductor devices can be integrated greatly depends on techniques for forming the patterns of features that constitute memory cells, i.e., fine pattern forming technologies. However, process equipment that can produce very fine patterns is extremely expensive and becomes increasingly expensive the finer the patterns to be produced become. Thus, the overhead associated with process equipment becomes cost-prohibitive when considering modifying or developing such equipment to increase the integration of, i.e., scale down, two-dimensional or planar semiconductor devices.
Three-dimensional (3D) semiconductor memory devices including three-dimensionally-arranged memory cells have been proposed to provide highly integrated devices that can be manufactured economically. However, there are still significant obstacles in manufacturing low-cost, 3D semiconductor memory devices, particularly in the mass-fabrication of 3D devices that possess or exceed the operational reliability of their 2D counterparts.